There is OpenFlow as a unified management mechanism in which a centralized controller performs multi-layer flow control. OpenFlow refers to a packet field and a rule which defines a flow with wildcards to identify the flow. Therefore, it is possible to control at a flow level.
In the operation of an information processing system using OpenFlow, a packet transmission path is switched at a high speed when a link failure occurs to make the system redundant.
A technique has been known in which a switch that has detected the occurrence of a link failure notifies a controller of the occurrence of the link failure and another switch inquires of the controller about the link failure and receives information about the link failure.
For example, the following technique has been known as a response to the occurrence of a link failure.
A switch which is the upper node of a link with a failure and a switch which is the lower node of the link detect the failure. The switch, which is the upper node, and the switch, which is the lower node, update information about the number of normal ports. The switch, which is the upper node, transmits the updated information about the number of normal ports to switches which are other adjacent lower nodes. The switch which is the lower node that detects the failure updates a packet transmission table on the basis of the updated number of normal ports.
[Patent Document 1] Japanese National Publication of International Patent Application No. 2004-522383
[Patent Document 2] Japanese Laid-open Patent Publication No. 2006-313949
[Patent Document 3] Japanese Laid-open Patent Publication No. 2007-208369
However, the above-mentioned technique has a problem that it is difficult to switch paths at a high speed when a failure occurs. In addition, the above-mentioned technique has a problem that it is difficult to switch paths considering the state of a link.